JP2009078941A - Additive for calcium aluminate hydraulic material, and cement composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an additive for an aluminate calcium hydraulic material which promotes the setting of a calcium aluminate hydraulic material with a sufficient degree, exhibits the effect of conversion suppression, and further can increase acid resistance and seawater resistance, and to provide a cement composition. <P>SOLUTION: The additive for a calcium aluminate hydraulic material comprises a substance obtained by subjecting lithium-containing ABW type zeolite to heating treatment at 300 to 650°C. In which, the content of lithium is ≥5% expressed in terms of Li<SB>2</SB>O, and the total content of Na<SB>2</SB>O and K<SB>2</SB>O is <0.5%. The cement composition contains the calcium aluminate hydraulic material and the additive to the calcium aluminate hydraulic material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention mainly relates to a calcium aluminate hydraulic material additive and a cement composition used in the civil engineering and construction industries.

Alumina cement is known along with Portland cement. Alumina cement is superior in sulfuric acid resistance to Portland cement and has a feature such as a low diffusion rate of chloride ions. This is because Portland cement is mainly composed of a calcium silicate compound, whereas alumina cement is mainly composed of a calcium aluminate compound. However, and CaO · _Al 2 _{O 3} calcium aluminate compound which is a main component of alumina _{cement, CaO · 2Al 2 O 3,} 12CaO · 7Al 2 O 3 is passed hydrated product generated hydration early time At the same time, it changes to a hydrate with a high density and causes so-called conversion that causes porosity and strength reduction, so it is not popular in the civil engineering and construction industry. As a method of suppressing this conversion, a method of using blast furnace slag, silica fume, or the like in combination has been proposed (Patent Document 1, Patent Document 2).

  On the other hand, it is also known to add a soluble lithium compound such as lithium carbonate or lithium hydroxide for the purpose of promoting the setting of alumina cement. However, these soluble lithium salts remarkably accelerate the setting and hardening of the alumina cement, and there is a problem that it is difficult to control. This is because lithium dissolves simultaneously with the kneading and promotes the setting of the alumina cement. For example, when 0.1% of lithium carbonate is added to alumina cement mortar having a setting time of about 3 hours, the setting is shortened to about 5 minutes. In addition, when the amount of lithium carbonate added is increased to 0.5%, almost instantaneous setting occurs. Thus, the soluble lithium compound remarkably promotes the hydration of the alumina cement and cannot obtain a reasonable pot life. Conversely, insoluble lithium compounds that do not release lithium at all do not provide a promoting effect. Therefore, a so-called sustained-release material that gradually releases lithium is desired. Further improvement of sulfuric acid resistance and seawater resistance is also desired.

  On the other hand, ABW type zeolite is known as a kind of zeolite containing lithium. This can be simply synthesized by using allophane as a raw material and allowing lithium hydroxide to act at a temperature within 100 ° C. However, no attempt has been made to add lithium-containing ABW-type zeolite to alumina cement. Furthermore, there is no examination about adding the heat-treated product to alumina cement. Also, it is not known at all what kind of effect can be obtained at that time.

  ABW-type zeolite is a zeolite containing lithium named for the first time reported by Barrer and White (Barrer RM and White ED, J. Chem. Soc). , 1951, 1267). That is, it is often written as A (BW) in the meaning of A of zeolite found by Barrer and White.

  Through a number of experiments, the inventors of the present invention have been able to moderately accelerate the condensation of calcium aluminate hydraulic materials such as alumina cement by heat-treating a specific lithium-containing zeolite and exhibiting the effect of suppressing conversion. The inventors have found that acid resistance and seawater resistance are improved, and have completed the present invention.

JP-A-60-180945 Japanese Patent Laid-Open No. 01-141844 Kono et al., Abstracts of 112th Academic Lecture Meeting of Inorganic Materials Society, pp. 8-9, 2006

  The present invention provides a calcium aluminate hydraulic material additive capable of moderately accelerating the setting of calcium aluminate hydraulic material, exhibiting the effect of suppressing conversion, and enhancing acid resistance and seawater resistance. To do.

That is, the present invention includes (1) a calcium aluminate hydraulic material additive containing a substance obtained by heat-treating lithium-containing ABW zeolite at 300 to 650 ° C., and (2) the lithium content is Li ₂ O equivalent (1) Calcium aluminate hydraulic material additive, which is 5% or more, (3) The total content of Na ₂ O and K ₂ O is less than 0.5% (1) or (2) A calcium aluminate hydraulic material additive, (4) a calcium aluminate hydraulic material, and a cement composition containing any one of (1) to (3) calcium aluminate hydraulic material additive, It is.

  The present invention provides an additive for a calcium aluminate hydraulic material that moderately accelerates the setting of the calcium aluminate hydraulic material, exhibits an effect of suppressing conversion, and can enhance acid resistance and seawater resistance. .

  In the present invention, “parts” and “%” are based on mass unless otherwise specified.

The calcium aluminate hydraulic material of the present invention is mainly composed of CaO and Al ₂ O ₃ and is not particularly limited. Specific examples _{thereof, CaO · 2Al 2 O 3,} CaO · Al 2 O 3, 12CaO · 7Al 2 O 3, 11CaO · 7Al 2 O 3 · CaF 2, 3CaO · Al 2 O 3, 3CaO · 3Al 2 Examples thereof include crystalline calcium aluminates represented as O ₃ · CaSO _{4 and the} like, and amorphous compounds mainly composed of CaO and Al ₂ O ₃ components. Among these, it is preferable from the viewpoint of securing the pot life to select one having a CaO / Al ₂ O ₃ molar ratio of 1 to 2.

Examples of a method for obtaining a calcium aluminate hydraulic material include a method in which a CaO raw material and an Al ₂ O ₃ raw material are heat-treated with a rotary kiln or an electric furnace. Examples of the CaO raw material for producing calcium aluminate include calcium carbonate such as limestone and shells, calcium hydroxide such as slaked lime, and calcium oxide such as quick lime. Examples of the Al ₂ O ₃ raw material include aluminum by-products in addition to industrial by-products called bauxite and aluminum residue ash.

When a calcium aluminate hydraulic material is obtained industrially, impurities may be contained. Specific examples _{thereof, SiO 2, Fe 2 O 3} , MgO, TiO 2, MnO, Na 2 O, K 2 O, Li 2 O, S, like P 2 _{O 5,} and F or the like. The presence of these impurities is not particularly problematic as long as the object of the present invention is not substantially impaired. Specifically, there is no particular problem if the total of these impurities is in the range of 10% or less.

Calcium aluminate hydraulic _{material, 4CaO · Al 2 O 3 ·} Fe 2 O 3, 6CaO · 2Al 2 O 3 · Fe 2 O 3, calcium such as _{6CaO · Al 2 O 3 · 2Fe} 2 O 3 alumino ferrite Calcium ferrite such as 2CaO · Fe ₂ O ₃ and CaO · Fe ₂ O ₃ , calcium aluminosilicate such as galenite 2CaO · Al ₂ O ₃ · SiO ₂ , anorthite CaO · Al ₂ O ₃ · 2SiO ₂ , melvinite 3CaO · MgO · 2SiO _2, Akerumanaito 2CaO · MgO · 2SiO _2, Monch celite CaO · MgO · SiO ₂ such as calcium magnesium silicate, tri-calcium silicate 3CaO · SiO _2, dicalcium silicate 2CaO · SiO _2, rankinite night 3Ca · 2SiO _2, calcium silicate such as Wollastonite CaO · SiO _2, calcium titanate CaO · TiO _2, free lime, leucite _{(K 2 O, Na 2 O} ) may contain · _{Al 2} O 3 · SiO 2, etc. is there. In the present invention, these crystalline or amorphous materials may be mixed.

The particle size of the calcium aluminate hydraulic material of the present invention is not particularly limited, but is usually in the range of 3000 to 9000 cm ² / g in terms of Blaine specific surface area, and about 4000 to 8000 cm ² / g. More preferred. If it is less than 3000 cm ² / g, strength development may not be sufficient, and if it exceeds 9000 cm ² / g, handling may be difficult.

The lithium-containing ABW zeolite of the present invention will be described.
Lithium-containing ABW-type zeolite was named after first reported by Barrer and White (Barrer RM and White ED, J. Chem. Soc., 1951, 1267). That is, it is often written as A (BW) in the meaning of A of zeolite found by Barrer and White. Here, the meaning of A will be supplemented. A is the first letter of the alphabet, meaning “found first” (respect: nomenclature and structure of zeolite, catalyst, Vol. 40, No. 3, pp. 185-190, 1998). Lithium-containing ABW-type zeolite has about 15 to 25% of crystal water. The SiO ₂ content and the Al ₂ O ₃ content are about 30 ± 5%, respectively.

  As a method for synthesizing a lithium-containing ABW-type zeolite, a method in which allophane is used as a raw material and reacting with lithium hydroxide has been known so far (Yusuke Okino et al. pp. 8-9, 2006).

  In the present invention, lithium-containing ABW-type zeolite synthesized by any method can be used. The additive of the calcium aluminate hydraulic material of the present invention (hereinafter referred to as additive) is obtained by heat-treating lithium-containing ABW zeolite. The heat treatment condition is preferably 300 to 650 ° C. If the heat treatment conditions are not within this temperature range, the effect of the present invention, that is, the condensation of the calcium aluminate hydraulic material is moderately promoted, the conversion suppressing effect is exhibited, and the effect of increasing acid resistance and seawater resistance is small. There is a case.

  The heat treatment referred to in the present invention is not particularly limited, but usually means a treatment such as drying or baking. As a specific method, for example, after allophane is reacted in a lithium hydroxide aqueous solution to produce ABW type lithium zeolite, heat treatment at 300 to 650 ° C. may be performed at the stage of drying operation. After drying at a temperature of less than 300 ° C, heat treatment may be performed again at a temperature of 300 to 650 ° C. As the drying device, a drum dryer, a shelf dryer, a cylindrical dryer, a rotary kiln, an electric furnace, or the like can be used.

When the lithium-containing ABW-type zeolite is heat-treated at 300 to 650 ° C., it changes to anhydrous ABW-type zeolite. That is, the crystal structure of the ABW type zeolite is maintained up to 300 ° C., and when the temperature exceeds 300 ° C., the crystal structure changes to a completely different crystal structure to become anhydrous ABW type zeolite. And it is in the state of anhydrous ABW type zeolite up to 650 ° C., but when it exceeds 650 ° C., it changes to γ-eucryptite. And when it heats further, it changes to (beta) -eucryptite at 900-1000 degreeC.
The heating time is preferably 5 minutes to 3 hours, more preferably 10 minutes to 2 hours. If the heating time is less than 5 minutes, the change to anhydrous ABW-type zeolite may not proceed sufficiently, and conversely, even if heated for more than 3 hours, the change to anhydrous ABW-type zeolite is sufficiently advanced. Therefore, it is uneconomical.

The lithium content of the additive of the present invention is not particularly limited, but is usually preferably 5% or more and more preferably 7% or more in terms of Li ₂ O. From the theoretical Si / Al molar ratio (= 1) of the zeolite, the lithium content is the maximum amount (13.5%) that can be supported in an amount corresponding to this charge balance. If the lithium content is less than 5%, there may be a case where a sufficient setting promoting effect and a conversion suppressing effect cannot be obtained.

The content of sodium or potassium in the additive of the present invention is not particularly limited, but usually, the total amount of Na ₂ O and K ₂ O is preferably less than 0.5%, 0.3 % Or less is more preferable. When the total amount of Na ₂ O and K ₂ O exceeds 0.5%, a sufficient setting acceleration effect may not be obtained.

Since the specific surface area of the additive of the present invention depends on the specific surface area of the lithium-containing ABW-type zeolite before the heat treatment, it is not uniquely determined. Usually, the BET specific surface area is 1 to 50 m ² / g. It is in the range.

  Although the usage-amount of the additive of this invention is not specifically limited, Usually, 1-50 parts are preferable in 100 parts of cement compositions which consist of a calcium aluminate hydraulic material and an additive, 3-40 parts Is more preferable, and 5 to 30 parts is most preferable. If the amount is less than 1 part, the effects of the present invention, that is, the effect of promoting condensation and the effect of suppressing conversion may not be sufficiently obtained, and even if the amount exceeds 50 parts, further enhancement of the effect cannot be expected. In addition, strength development may be reduced.

  The additive and cement composition of the present invention may be mixed at the time of construction, or a part or all of them may be mixed in advance.

  In the present invention, fine aggregates such as sand, coarse aggregates such as gravel, expanded materials, quick hard materials, water reducing agents, AE water reducing agents, high performance water reducing agents, high performance AE water reducing agents, antifoaming agents, and thickeners. And various additives such as clay minerals such as polymer emulsion, setting agent, bentonite, anion exchanger such as hydrotalcite, blast furnace granulated slag fine powder and blast furnace slow cooling It is possible to use one or more of the group consisting of slag fine powder, limestone fine powder, admixture materials such as fly ash and silica fume, etc. in a range that does not substantially impair the object of the present invention. .

"Example 1"
Various lithium-containing ABW-type zeolites and calcium aluminate hydraulic materials (a) were blended in the proportions shown in Table 1 to prepare cement compositions. To 100 parts of the cement composition, 200 parts of fine aggregate and 40 parts of water were blended and mixed to prepare a mortar. Using this mortar, the setting time, compressive strength, sulfuric acid resistance and seawater resistance were evaluated. In addition, in order to confirm the effect of conversion, an accelerated conversion test was conducted to confirm the state of strength reduction. As a comparative example, the same test was performed for lithium carbonate and commercially available Ca-type zeolite. The results are shown in Table 1.

<Materials used>
Calcium aluminate hydraulic material A: Commercially available alumina cement, manufactured by Denki Kagaku Kogyo Co., Ltd., and mainly composed of CaO.Al ₂ O ₃ . Blaine specific surface area 5000 cm ² / g.
Heat-treated product A of lithium-containing ABW-type zeolite: heat treatment temperature 400 ° C., Li ₂ O content is 9% in terms of Li ₂ O, and the total content of Na ₂ O and K ₂ O is less than 0.5%.
Heat-treated product B of lithium-containing ABW-type zeolite: heat treatment temperature 400 ° C., Li ₂ O content is 5% in terms of Li ₂ O, and the total content of Na ₂ O and K ₂ O is less than 0.5%.
Heat-treated product C of lithium-containing ABW-type zeolite: heat treatment temperature 400 ° C., Li ₂ O content is 7% in terms of Li ₂ O, and the total content of Na ₂ O and K ₂ O is less than 0.5%.
Heat-treated product D of lithium-containing ABW-type zeolite: heat treatment temperature 400 ° C., Li ₂ O content is 11% in terms of Li ₂ O, and the total content of Na ₂ O and K ₂ O is less than 0.5%.
Heat-treated product E of lithium-containing ABW zeolite: heat treatment temperature 300 ° C., Li ₂ O content is 9% in terms of Li ₂ O, and the total content of Na ₂ O and K ₂ O is less than 0.5%.
Heat-treated product F of lithium-containing ABW-type zeolite: heat treatment temperature 500 ° C., Li ₂ O content is 9% in terms of Li ₂ O, and the total content of Na ₂ O and K ₂ O is less than 0.5%.
Heat-treated product G of lithium-containing ABW-type zeolite: heat treatment temperature 650 ° C., Li ₂ O content is 9% in terms of Li ₂ O, and the total content of Na ₂ O and K ₂ O is less than 0.5%.
Lithium carbonate (Li ₂ CO ₃ ): Commercial product, reagent grade 1 type Ca-type zeolite: trade name “Alcat”, fine aggregate manufactured by Nippon Chemical Industry Co., Ltd .: Himekawa, Niigata Prefecture, specific gravity 2.64.
Water: tap water

<Measurement method>
Setting time: 200 cc of mortar was put into a plastic cup, the surface other than the upper surface was insulative, and the mortar temperature was measured with a thermocouple. The time at which the temperature rose by 2 ° C. from the kneading temperature was defined as the setting time.
Compressive strength: A molded body of 4 cm × 4 cm × 16 cm was prepared by filling a mortar into a mold, and the compressive strength at the age of 28 days was measured according to JIS R 5201.
Sulfuric acid resistance: A mortar specimen for measuring compressive strength at the age of 28 days was immersed in a 5% strength sulfuric acid solution for 3 months, and acid resistance was evaluated from the sulfuric acid penetration depth. X is when the sulfuric acid penetration depth is 5 mm or more, Δ is when the sulfuric acid penetration depth is 3 mm or more and less than 5 mm, and ◯ is when the sulfuric acid penetration depth is less than 3 mm. The sulfuric acid penetration depth was evaluated by the phenolphthalein method. This is based on the fact that the pH of the portion infiltrated with sulfuric acid is lowered, so that it does not show a color reaction due to phenolphthalein.
Seawater resistance: A mortar specimen for measuring compressive strength was subjected to water curing at 20 ° C. until the age of 28 days, and then the specimen was immersed in simulated seawater for 4 weeks. Seawater resistance was evaluated by measuring the penetration depth of chloride ions. The penetration depth of chloride ions was confirmed by the fluorescein-silver nitrate method.
Accelerated conversion test: The mortar specimen for compressive strength measurement was cured in water at 20 ° C. until the age of 28 days, and then the compressive strength was measured after sealing the specimen and curing at 50 ° C. for 14 days. The relative value when the compressive strength at the age of 28 days is defined as 100 is shown.

<Synthesis and heat treatment of lithium-containing ABW-type zeolite>
EDI type zeolite containing lithium was synthesized by reacting allophane and lithium hydroxide as raw materials in water. In this _case, the Li 2 _O / _Al 2 O ₃ molar ratio varied from 0.5 to 4.0, changing the content of Li ₂ O. The SiO ₂ / Al ₂ O ₃ molar ratio was fixed at 1.73, the reaction temperature was 90 ° C., the reaction time was 48 hours, and the reaction was conducted while stirring. The obtained composite was separated into solid and liquid, washed with warm water at 60 ° C., and dried at 70 ° C. Allophane was used in an amount of 10 kg, and lithium hydroxide was dissolved in water. The lithium hydroxide solution was 100 kg. As a result of identifying the synthesized product by powder X-ray diffraction, it was an ABW type zeolite. Further, the lithium-containing ABW-type zeolite was heat-treated at a temperature range of 300 to 650 ° C. to obtain a heat-treated product of lithium-containing ABW-type zeolite. The heat treatment time was 1 hour.

<Materials used for the synthesis of zeolite>
Allophane: water-purified product from Tochigi Prefecture, commercial product, SiO ₂ content 33.6%, Al ₂ O ₃ content 33.1%, Fe ₂ O ₃ content 2.3%, CaO content Amount 0.4%, MgO content 0.1%, Na ₂ O content 0.03%, K ₂ O content 0.02%, ignition loss 30.1%.
Lithium hydroxide: Commercial product.
Water: tap water

  From Table 1, it is clear that the additive of the present invention moderately accelerates the setting of the calcium aluminate hydraulic material, has an effect of suppressing conversion, and improves sulfuric acid resistance. And the effect becomes more remarkable when there is much usage-amount of an additive.

"Example 2"
A cement composition was prepared by blending 20 parts of heat-treated lithium-containing ABW zeolite and 80 parts of calcium aluminate hydraulic material, and the types of calcium aluminate hydraulic material were changed as shown in Table 2. Except that, the same procedure as in Example 1 was performed. The results are also shown in Table 2.

<Materials used>
Calcium aluminate hydraulic material b: 12CaO · 7Al ₂ O ₃ , reagent primary calcium carbonate and aluminum oxide are mixed at a molar ratio of 12 to 7 and baked at 1350 ° C. for 3 hours twice. Synthesis. Blaine specific surface area 5000 cm ² / g.
Calcium aluminate hydraulic material c: Amorphous 12CaO · 7Al ₂ O ₃ , 3% reagent grade silica added to calcium aluminate broth, melted at 1650 ° C., and then rapidly cooled to synthesize. Blaine specific surface area 5000 cm ² / g.
Calcium aluminate hydraulic material D: Reagent grade calcium carbonate and aluminum oxide are mixed so that the molar ratio of CaO.2Al ₂ O ₃ and CaO / Al ₂ O ₃ is 0.5, and calcined at 1500 ° C. for 3 hours. This process is repeated twice. Blaine specific surface area 5000 cm ² / g.
Calcium aluminate hydraulic material E: Mixture of 3CaO · Al ₂ O ₃ and 12CaO · 7Al ₂ O ₃ , reagent grade calcium carbonate and aluminum oxide so that the CaO / Al ₂ O ₃ molar ratio is 2.5 The process of mixing and baking at 1350 ° C. for 3 hours was repeated twice. Blaine specific surface area 5000 cm ² / g.

From Table 2, it is clear that the additive of the present invention moderately accelerates the setting of the calcium aluminate hydraulic material, has an effect of suppressing conversion, and improves sulfuric acid resistance. It can be seen that the effect is more remarkable as the calcium aluminate hydraulic material has a smaller CaO / Al ₂ O ₃ molar ratio.

  The additive of the present invention moderately accelerates the setting of the calcium aluminate hydraulic material, exhibits the effect of suppressing conversion, and further can enhance acid resistance and seawater resistance. Objects can be widely used in the civil engineering and construction fields.

Claims (4)

An additive for a calcium aluminate hydraulic material containing a substance obtained by heat-treating lithium-containing ABW-type zeolite at 300 to 650 ° C. The content of lithium, additive calcium aluminate hydraulic material according to claim 1 is 5% or more by Li 2 _O conversion. The additive of calcium aluminate hydraulic material according to claim 1 or 2, wherein the total content of Na ₂ O and K ₂ O is less than 0.5%. The cement composition containing a calcium aluminate hydraulic material and the additive of the calcium aluminate hydraulic material of any one of Claims 1-3.